I remember a glass device my physics teacher had at high school which

  1. Contained some vanes mounted somehow on a vertical axis, which were all black on one side and white on the other
  2. Was in a vacuum (partial, at least)
  3. Caused the vanes to spin when a light was shone onto them

I've never seen such a device since. Can anyone tell me if it has a name?

  • $\begingroup$ For UK readers, Crookes Radiometers used to be on sale in the Science Museum Shop [ sciencemuseumshop.co.uk/home.html#1 ] in South Kensington, London. Searching on that web site, I can find no sign of them there this year; but there are plenty of other gadgets and ideas for Christmas presents to stimulate the interest of young possible future Nobel prize winners ;-P $\endgroup$ – John R Ramsden Nov 25 '12 at 12:57

Yes, it is called a Crookes radiometer or a light mill.

  • 2
    $\begingroup$ I've edited it to say "Crookes radiometer", as there are other types of radiometer that work differently. I hope that's OK. $\endgroup$ – Nathaniel Nov 25 '12 at 8:59

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